Conventionally, farmers and turf maintenance people have, for the most part, incorporated substances such as fertilizers, insecticides and polymers into the soil using tillage tools that mechanically cut through the ground and release the additive products at a point below the top surface of the ground. Surface treatment may also be carried out by either spraying liquid chemicals onto the top surface of the ground or spreading dry materials on the surface without making efforts to incorporate them deeper into the soil.
However, using tillage tools to plow through the soil in order to deliver the substances to the subsurface causes significant soil eruption and surface disturbance, as well making substantial openings in the ground. This is obviously unacceptable on homeowner lawns, golf greens, tee boxes and other areas of golf courses because it prevents recreational use of such areas for a significant amount of time following such procedures. Top surface application of chemicals runs the risk of environmental impairment due to run off and air-borne contamination.
While a significant amount of technology currently exists for placing liquid substances into the subsurface using high pressure water jets that cut through the soil and carry the substance down to the desired depth, very little successful work has been done in the placement of dry, granular materials without using mechanical tillage devices. Although various attempts have been made to deliver the dry materials to the subsurface using high pressure liquid jets, such efforts have achieved only mixed results at best.
One reason for this apparent lack of success is the fact that many granular materials, when mixed with water, become highly corrosive and injurious to the mechanisms used to apply them. Furthermore, granular materials are inherently abrasive so as to produce untoward wear in mechanical components if not properly handled.
Moreover, dry, granular materials are difficult to meter accurately unless the metering mechanism is kept in a moisture-free environment. Even then, a metering mechanism which is sensitive enough to allow minute adjustments in the application rate of granular additives is difficult to obtain.